Pulping apparatus

ABSTRACT

A pulping tank is provided, for the pulping of solid debris in a liquid medium, with a rotating impeller being used to impel liquid and sized particles outwardly through a sizing ring, with the impeller carrying means for cutting debris into desirably sized particles, and with the impeller being positioned at the lower end of the sizing ring in such a manner as to control an opening therebetween, for the passage of particles therethrough, into contact with cutting teeth. The cutters may be applied to the impeller plate by any of several techniques, as for example by being removably secured thereto. Also, certain tank designs facilitate the formation of especially desirable vortex arrangements of a slurry being pulped, during rotation of the impeller at desired speeds.

United States Patent 1191 Craig et al. 1 Jan. 30, 1973 541 PULPING APPARATUS $578,250 5 1071 (6111mm :11 ..241 46.11

[75] lnvemors: 333:2 gt gii gzi rf Primary Examiner-Granville Y. Custer .lr.

Attorney-Paul & Paul Wayne T. Buckman, P1persv1lle, Pa.

[73] Assi nee: Wascon S stems, Inc., Hatboro, Pa. [57] ABSTRACT [22] Filed: Aug. 6, 1970 A pulping tank is provided, for the pulping of solid debris in a liquid medium, with a rotating impeller [Zll (L608 being used to impel liquid and sized particles outwardly through a sizing ring, with the impeller carry- 1521 Us. c1. ..241/46.11, 241/4617, 241/73, s means for cutting debris into desirably Sized P 24|/294 cles, and with the impeller being positioned at the 151 11111.01 ..B02 13/18 lower end of the sizing ring such a manner as to 158 Field Of Search ..241/46 46.06 46.11 46.17 Opening thcrebctween, Passage of 24 74 134 particles therethrough, into contact with cutting teeth. The cutters may be applied to the impeller plate by any of several techniques, as for example by being [56] References Clted removably secured thereto. Also, certain tank designs UNITED STATES PATENTS facilitate the formation of especially desirable vortex arrangements of a slurry being pulped, during rotation Wandel X of the ener at desired S eeds 3,009,656 11/1961 Martindale ..24l/46.l7 p p 2.9l9,075 12/1959 Pfeiffer ..24l/294 X 18 Claims, 6 Drawing Figures plate and the sizing ring.

PULPING APPARATUS BACKGROUND OF THE INVENTION In the past, various pulping apparatus and techniques have been developed for handling waste disposal, on a large scale, as for example, for institutional use such as business offices, hospitals, and the like. Such apparatus and techniques have generally involved the use of pulping tanks, with sizing screens at the bottom thereof, and with impeller plates rotatable within the tank, for impelling liquid and desirably sized debris outwardly through the holes of the sizing ring. Such techniques have been highly desirable, in many instances. However, for certain types of debris, such as rubber and plastic tubing, hose and the like, the impeller tends to impel such debris for great periods of time within the pulping tank, without reducing it in size, sufficient to pass through the holes of the sizing ring. Often, such tubing and the like is several inches in length, and because of the natural resilience and tendency to bounce, of such material, comminution of the same becomes difficult, particularly if it is desired that the material be rapidly pulped. Accordingly, there has arisen a need for handling resilient tubing, hose and the like, as well as other types of particles, in a manner different than the manner in which the bulk of debris is handled within the pulper.

Also, in pulper development, it has been found that some debris components, such as rags and the like, tend, upon rotation of the impeller, to find their way to the center of the impeller, just above the axis of rotation thereof, and there such debris remains, to become bailed-up", in that, at the center of the impeller, it is a not subjected to radially outwardly directed impelling forces, and further it is not subjected to cutting, tearing, 1 abrading and the like. Accordingly, there has developed a need for maintaining debris particles that are to be pulped in the pulper, at locations remote from directly above the center of the rotating impeller,

With the manufacture of impeller plates, wherein cutting teeth are brazed directly thereon, if sufficient care is not .taken, the heat of brazing or liketoothsecuring process may introduce sufficient heat to the impeller plate, that such plate becomes warped, and thereby possibly not running true, as for example, than rotating in a'wobbling fashion. Accordingly, there has arisen a'need'to prevent warping of impeller plates as a result of cutting tooth securement thereto.

JSUMMARY 0F This INVENTION The present invention is directed toward overcoming the problems and satisfying the needs set forth above. Accordingly, the impellerplate is disposed with its upper central surfaceslightly below the sizing ring, to facilitate the passage of tubing and the like between, a passage zone that may be carefully controlled, with teeth being provided carried by a lower annular exten: sion of the impeller plate, and by the lower end of the sizing ring, respectively, for cutting tubing andlthe like that pass between the upper portion of the impeller Furthermore, modifications are made to the pulping tank itself, such that rags. and the likewill be maintained within the vortex of pulped liquid, but radially, outwardly of the centerof the rotating impeller, by making tankmodifications that will enablethe'vortex embodiments and-the appended claims. i

of pulped liquid-in the tank, to have a central recess that extends downwardly to the upper surface of the impeller plate, and at this point to have a diameter sufficiently large that it takes in the central untoothed portion of the impeller plate, such that all swirling rotating water within the vortex (outside the central depression) is in a zone disposed above cutting teeth, or radially outwardly thereof. The changes made to the impeller tank in this regard may comprise a squaring-off of the tank bottom wall in relation to upstanding cylindrical tank walls, and/or may comprise the insertion of an upstanding band or plate sections thereof, generally parallel to the upstanding sidewall of the tank.

Warping of the impeller plate :is prevented by removablysecuring impeller teeth thereto, as by first brazing or otherwise securing the impeller teeth to individual smaller plate sections, with such sections being bolted onto the impeller plate, or by brazing the cutting teeth to heads of screws, bolts or the like, which are then threaded into the impeller plate.

Accordingly, it is a primary object of this invention to provide a novel flow passage within a pulping tank, whereby the flow of certain particles would be radially outwardly, acrossthe impeller plate, underthe sizing ring, for shredding between teeth carried by the sizing ring and by downwardly stepped portions of the impeller plate. I 7

It is a further object of this invention to provide a novel impeller plate design and location, for achieving a predetermined flow path of certain particles radially outwardly of the impeller plate, and beneath the sizing ring.- v

It is a further object of this invention to provide, in a pulping tank, meansfor impelling debris such that it does not accumulate abovethe center of the impeller plate, during rotation of the impeller plate.

It is another object of this invention to provide novel methods of securing cutting teeth to impeller plates that will eliminate warping of the impeller plates.

Other objects and advantages of the present invention will be readily apparent to those skilled in the art from a reading of the following brief description of the drawing figures, detailed descriptions of the preferred 'In the drawings:, I FIG. I afragrnentary vertical, sectional view of a pulping tank of this invention ,with the vortex of pulped liquid that is formed upon rotation of the impeller at a desired speed being indicated in full lines, and with dotted lines indicatingiavortex of theprior art type, taken generally along the l'ine'l I of FIG. 2.

- FIG. 2 is a'horizontal'sectional view,-taken throughthe pulping tank of FIG. 1, with many of the components inside the tank being illustrated in top plan FIG. 3is'a fragmentary side elevational view of a por tion of the sizing ring. and a ,vortex panel carried thereby, taken generally along the line III--III of FIG.

FIG. 4 is a fragmentary top planviewjofan impeller plate having screws with toothed 'heads threaded therein, as 'a modified form of .tooth attachment to that illustrated injFIG. 2. I c

FIG. 5 is a fragmentary vertical sectional view of a screw with tooth attached thereto, as illustrated in FIG.

4, taken generally along the line /---V of FIG. 4.

FIG. 6 is a view generally similar to that of FIG. 1, but wherein the tank bottom configuration for creating a desired vortex of fluid impelled therein is illustrated in a novel arrangement.

Referring now to the drawings in detail, reference is first made to FIG. 1, wherein there is illustrated'a pulping tank, generally designated by the numeral 10. The tank 10 includes an upstanding cylindrical sidewall 11, which merges into a downwardly sloped inner annular protrusion 12, which comprises the tank bottom wall. An annularly configured sizing ring 13 is provided, carried by the bottom wall 12. The sizing ring 13 includes an upper flange 14, bolted or otherwise suitably secured to the radially innermost end of the bottom wall 12, and has connected thereto a cylindrical perforated portion 15, having a plurality of holes 16 therein, of a selected predetermined size, in order to permit the passage therethrough of debris particles that have been pulped and comminuted to size, such particles being carried through the holes 16 in a water medium that is contained withinthe tank 1 l. The sizing ring 13 carries, at its lower end, a shape-retaining ring portion 17, which is also annular, and which is fitted over the lower end of the cylindrical ring portion 15, and secured thereto by some suitable means, such as welding or the like.

An impeller plate 20 is mounted at the bottom of the interior of the tank 10, with its upper surface 21 disposed just below the lower surface 22 of the sizing ring 13.

The impeller plate 20 is mounted on a shaft 23, for rotation therewith, with the shaft 23 passing downwardly through a discharge cavity bottom wall 24, and being sealed by a suitable packing 25. Thus, beneath the plate 20 there is defined a discharge cavity 26, by the wall 24 and by an upwardly sloped annular wall portion 27, with the discharge cavity 26 merging into a discharge duct 28, for discharge of pulped particles and liquid rightward, as viewed in FIG. 1.

The impeller plate 20 comprises a base plate portion 30 which is secured to a supporting plate 31 by suitable screws, with the supporting plate 31 being press-fit or otherwise suitably carried by the shaft 23. A plurality of pie-shaped plate sections 33 are arranged, as for example eight in number, as view in FIG. 2, to comprise when taken together, a generally circular arrangement, as viewed in FIG. 2, with the plate sections 33 being fastened to the base plate 30 by suitable screws 34, disposed in clearance holes 35 in the plate sections 33, for sinking the heads of the screws 34. An upper plate 36 is provided, clamped over the radial innermost ends of the plate sections 33, by means of a washer 37 and cap-headed screw 38, passing through the plate 36, and being threaded into the upper end of the shaft 23.

A plurality of cutting teeth 40 are provided, such teeth 40 being generally constructed in accordance with the disclosure of similar teeth in US. Pat. No. 3,489,356, issued .Ian. 13, 1970, the disclosure of which is hereby incorporated herein. Also, a plurality of ski-blocks 41, with teeth 40 carried thereon are provided, with the ski-blocks 41 being constructed generally as described in application 'Ser. No. 763,620, filed Sept. 30, 1968, as are retarder plates 42 carried by the tank bottom wall 12, also for the purpose described in application Ser. No. 763,620, for cooperation with the teeth 40 on the ski-blocks 41, for effecting a scissors-like cutting action of debris impelled therebetween. Thus, the retarder plates 42 are mounted on the tank bottom wall 12 by suitable bolts 43, and the ski-blocks 41 are welded to or otherwise suitably carried by the plate sections 33.

A plurality of bottom vanes 44 are carried at the lower end of the impeller plate 20, in the discharge cavity 26, in order to facilitate the circulation and discharge of slurry toward the outlet duct 28, after its passage into the chamber 26.

An annular ring-like plate 45 is mounted on and comprises a part of the impeller plate 20, with the plate 45 being carried by the lower end of the plate 20, and being secured thereto by any suitable means, as by bolting or welding the same thereon.

The ring 45 comprises a radial outward extension of the impeller plate 20, and has an upper surface 46 that is disposed substantially lower than the upper surface 21-of the impeller plate inner or central portion, in that the ring portion 45 extends beneath the sizing ring 13, whereas the generally central portion 29 of the impeller plate is of an outer diameter less than the inner diameter of the sizing ring lower portion 17. Thus, there is a stepped relationship between the surfaces 21 and 46 of the impeller plate. The bottom of the sizing ring portion 17 carries a plurality of teeth 47, which extend downwardly therefrom. A plurality of teeth 48 are carried by the impeller plate portion 45, and extend up wardly therefrom, as illustrated in FIG. 1, in order to cooperate with the teeth 47, to effect a scissors-like cutting action therebetween, with the teeth 47 and 48 being mounted respectively to define loci of points having differently sized circumferences, as for example, with the teeth 48 describing a greater circle than the teeth 47, in order that adjacent sloped surfaces 51 and 50, respectively, may define a cutting zone therebetween, upon rotation of the impeller plate 20. The teeth 47 and 48 are constructed generally similar to the teeth 40. It will be seen, that with the arrangement illustrated in FIG. 1, the distance D between the inner lower edge of the sizing ring 13 and the outer upper edge of the inner portion 29 of the impeller plate 20 may be carefully controlled, to any desired dimension, in-order to predetermine the size of particles that will be impelled radially outwardly across the upper surface 21 of the impeller plate 20, but beneath the sizing ring 13, to be engaged between cooperating teeth 47 and 48, and cut thereby. The adjustmentof the elevation of the impeller plate 20 may be made by any suitable means, to obtain the desired distance D indicated. It will be clear that tubing, hose and like particles of rather long length (greater than several inches or more), but of a diameter determined by the distance D may pass straight outward radially across the upper surface of the impeller plate 20, and through the zone identified by the letter D, to be shredded by the teeth 47 and 48, and then to pass into the discharge cavity 26, for subsequent discharge through the duct 28. For example, the distance D may preferably be within the range three-sixteenths to one-fourth inches for a certain size hospital tubing and the like that are desired to be passed therethrough.

The plate sections 33 have the teeth 40 brazed thereto. By brazing the teeth 40 to the plate sections 33, as opposed to brazing the teeth 40 directed to the plate 30, the smaller arcuate sections 33 would not, individually, be prone to distortion to the extent that a large plate 30 would distort under the heat of brazing, and furthermore, the thinner center plate sections 33 would become flattened-out upon tightly bolting the same to the heavier plate portion 30. Thus, the dimension D may be held, without a wobbling that may otherwise be attendant to the use of a warped plate for an impeller.

In the embodiment of FIG. 1, there is illustrated a vortex-altering band 54 which is bolted to the bottom wall 12 by suitable bolts or screws 55, as illustrated in FIGS. 1 and 2.

The band 54 is generally arcuate in configuration as viewed in plan (FIG. 2), and has a plurality of flanges S6 to facilitate its securement to the tank bottom wall 12. The use of the band 54 as illustrated in FIG. 2, in conjunction with a sloped bottom wall 12, as discussed above, at a given speed of rotation for the impeller plate 20, such as a peripheral speed of the outer radial end of the central portion 29 of the impeller 20 of 3,200 feet per minute, approaches the effect of a tank construction having a bottom wall at right angles to the cylindrical side wall and will cause the vortex formed in the liquid slurry within the tank 10 to be changed from the configuration illustrated in dotted lines in FIG. 1, to the configuration substantially as illustrated in full lines therein, such that a vortex configuration 60 is formed, having a central cavity 61 that extends completely downwardly to the upper surface of the impeller plate 20, and which, during rotation of the impeller plate at the desired pre-selected speed for any given pulping tank, will be of a sufficient diameter X at the junction of such vortex with the impeller plate 20, that the central-most portion of the impeller plate 20, which is free of cutting teeth thereon, will not be traversed with debris or liquid, such that all debris will follow a path outside the zone indicated by X in FIG. 1, across cutting teeth 40 disposed outside the zone X, whereby such debris particles may be shredded, severed, and the like by the teeth 40 on the impeller plate 20, by the skiblocks 41 and retarder plates 42, and teeth 40 carried thereon, and by teeth 40 that may optionally be provided on the various surfaces of the band 54. It will thus be seen that the path of motion of debris in its carrying liquid (water) under rotational motion provided by the impeller 20, will not traverse the central portion of the impeller plate 20 defined by the zone X.

With particular reference to FIG. 6, there is illustrated a pulping tank generally designated by the numeral 70, and comprising an upstanding generally cylindrical sidewall 71, having an annular bottom wall 72, protruding radially inwardly thereof, with the bottom wall 72 being substantially normal, or at right angles to the sidewall 71.

A sizing ring 73 of identical construction to the sizing ring 13 of FIG. 1 is provided, with the exception that the upper flange 74 thereof is also at right angles to the annular perforated portion 75, for facilitating the securement of the sizing ring 73 to the bottom wall 72, by any suitable means, such as by the bolts 76.

The remainder of the construction of the tank 70 is similar to comparable portions of the tank 10 of FIG. 1, as is the construction of the various other impeller features such as those that will provide a passage D, and

sizing ring construction of the embodiment of FIG. 6 similar to equivalent features of the embodiment of FIG. I, and therefore detailed discussion of these similar components need not be repeated herein. It will be noted that, by making the bottom wall 72 to be substantially at right angles to the sidewall 71, a vortex 77 is achieved that is substantially similar to the vortex 60 of the tank of FIG. 1, in that the vortex 77 has a central void or opening 78 that, under an impeller speed that has been pre-selected such as a peripheral speed of 4,000 feet per minute for the upper portion of the impeller 79. The untoothed central portion of the impeller plate 79 is not covered by the pulped slurry, but only the outer toothed portions of the impeller plate 79 are covered by the pulped slurry, as illustrated in FIG. 6, such that balled-up rags and the like will not accumulate at the zone 78, above the central portion of the impeller plate 79.

A plurality of panels 80 of generally arcuate configuration are also preferably provided. These panels 80 each have an L-shaped cross-sectional configuration with legs 81 to facilitate their securement to the tank bottom wall 72. The upstanding cylindrical portions 83 of the panels 80 are sloped upwardly from the tank bottom wall 72 (or from the upper flange 74 of the sizing ring 73), as illustrated in FIG. 3, with the sloped surface 82 thereof terminating in an abrupt end 83. The panels 80 are disposed at several locations, equidistantly radially from the center of rotation of the impeller 79, with all such panels 80 cooperating to define, in' the aggregate, an incomplete or segmented band about the inner end of the bottom wall 72 of the tank 70. The surfaces 82 of the panels 80 are sloped in order to permit debris to slide thereover rather than becoming caught thereon as debris is impelled in the circular motion about the interior of the tank 10. The arcuate panels 80 also have teeth 40 thereon which provide additional abrading means higher in the tank 70, and would also therefore facilitate pulping, as to the teeth 40 on the band 54 of FIG. 1. Furthermore, the upstanding panels 80 also add to the formation of the desired vortex 77, when such panels 80 are used.

With reference to FIGS. 4 and S, an alternative im peller plate is illustrated, as comprising 'a raised inner portion 91, generally similar to that 29 of FIG. 1, and having an outer ring-like portion 92, having a surface 93 at a lower level than the surface 94 of the portion 91, also generally similar to the embodiment of FIG. 1. A plurality of teeth 95 are also provided on the upper surface 93 of the portion 92.

A plurality of screws 96, having hex or equivalent bolt heads 97 are threaded into tapped holes 98 of the plate portion 91, with the heads 97 having previously brazed thereto teeth 100, substantially identical to the teeth 40 of FIG. 2. Thus, by brazing the teeth 100 to the screw heads 97, warping of the impeller plate portion 91 is prevented, in addition to making the teeth 100 readily removable from the plate 91, for replacement or the like, as desired.

It will be apparent from the foregoing that various modifications may be made in the details of construction of the various aspects of the apparatus of this invention, all within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. In a pulping tank adapted for the pulping of debris and the like, comprising pulping tank means for receiving debris and liquid therein, sizing ring means carried by and disposed annularly at the bottom of the tank for permitting the passage radially outwardly therethrough of desirably sized pulped debris, said sizing ring means having a plurality of holes therethrough of predetermined size, generally horizontal impeller plate means disposed at the bottom of said tank means and having cutting elements on an upper surface thereof for impelling debris therein with rotary motion of said impeller means, radially outwardly through holes in said sizing ring means, an uppermost surface portion of said impeller plate means being disposed lower than said sizing ring means, inwardly of said sizing ring means with downwardly extending cutting means being carried by said sizing ring means and cutting means being carried by said impeller means, and with said disposition of said impeller plate upper surface and said cutting means defining means facilitating the passage of debris particles in radially directed straight lines across said plate means upper surface and under said sizing ring means through a cutting zone defined by said cutting means.

2. The apparatus of claim 1, wherein said sizing ring means comprises an annular screen having an annular shape-retaining ring carried at the lower end thereof.

3. In a pulping tank adapted for the pulping of debris and the like, comprising pulping tank means for receiving debris and liquid therein, sizing ring means carried by and disposed annularly at the bottom of the tank for permitting the passage radially outwardly therethrough of desirably sized pulped debris, said sizing ring means having a plurality of holes therethrough of predetermined size, impeller plate means disposed at the bottom of said tank means for impelling debris therein with rotary motion of said impeller means, radially outwardly through holes in said sizing ring means, an uppermost surface portion of said impeller plate means being disposed lower than said sizing ring means, inwardly of said sizing ring means with downwardly extending cutting means being carried by said sizing ring means and cutting means being carried by said impeller means, and with said disposition of said impeller plate upper surface and said cutting means defining means facilitating the passage of debris particles in radially directed straight lines across said plate means upper surface and under said sizing ring means through a cutting zone defined by said cutting means, wherein said impeller plate means comprises a vertically stepped plate, with an annular outermost portion having an upper surface disposed lower than said uppermost surface portion of said impeller plate.

4. The apparatus of claim 3, wherein said cutting means carried by said impeller means and said sizing ring means comprise oppositely directed teeth mounted with their apices to each respectively define a locus of points, each such locus of points describing a circle of different diameter.

5. The apparatus of claim 3, wherein the distance between the circumferential inner and lower edge of said sizing ring means and the circumferential outer edge of said uppermost surface portion of said impeller plate means is of a predetermined dimension selected in accordance with the maximum size of particles desired to be passed therebetween.

6. The apparatus of claim 4, wherein the distance between the circumferential inner and lower edge of said sizing ring means and the circumferential outer edge of said uppermost surface portion of said impeller plate means is of a predetermined dimension selected in accordance with the maximum size of particles desired to be passed therebetween.

7. The apparatus of claim 5, wherein said distance is approximately one-fourth inch.

8. The apparatus of claim 5, wherein said distance is approximately three-sixteenths inch.

9. A pulping tank adapted for the pulping of debris and the like, comprising a container having an upstanding cylindrical wall and an incomplete bottom wall comprising an annular radially inwardly directed protrusion from said cylindrical wall, with a rotatably driveable impeller plate disposed substantially inwardly thereof and spaced below said protrusion, with a perforated sizing ring between said plate and protrusion for passing therethrough particles impelled outwardly upon rotation of said plate, said impeller plate being provided with abrading teeth disposed on the upper surface thereof, comprising an outer annular abrading surface portion located outwardly of a non-abrading central portion of said plate, including means comprising a component of said tank for creating a predetermined liquid vortex in the tank upon rotation of said impeller plate at a predetermined speed, such that the vortex has a central cavity, the bottom of which extends to the impeller plate and defines an area greater than said non-abrading portion of said plate.

10. The apparatus of claim 9, wherein said abrading surface portion comprises a toothed surface portion, and said non-abrading portion comprises an untoothed portion.

11. The apparatus of claim 9, wherein said latter means comprises said incomplete bottom wall being substantially normal to said upstanding cylindrical wall.

12. The apparatus of claim 9, wherein said latter means comprises projection means upstanding from inner portions of bottom wall.

13. The apparatus of claim 11, including projection panel means upstanding from inner portions of said bottom wall, wherein said projection panel means comprises a plurality of individual members protruding upwardly from said bottom wall, each having upper surfaces sloped upwardly from the bottom wall to free ends thereof, with said sloped surfaces facing in opposition to the predetermined direction of debris travel in the tank comprising means facilitating travel of debris over said members, with said members being circumferentially arranged on said bottom wall.

14. in a pulping tank adapted for the pulping of debris and the like, comprising pulping tank means for receiving debris and liquid therein, sizing ring means carried by and disposed annularly at the bottom of the tank for permitting the passage radially outwardly therethrough of desirably sized pulped debris, said sizing ring means having a plurality of holes therethrough of predetermined size, impeller plate means disposed at the bottom of said tank means for impelling debris therein with rotary motion of said impeller plate means, radially outwardly through holes in said sizing ring means, an uppermost surface portion of said impeller plate means being disposed lower than said sizing ring means, inwardly of said sizing ring means with plate having a centrally disposed drive shaft connected i0 thereto, and cutting members replaceably carried by said plate.

15. The apparatus of claim 13, wherein said cutting members are connected to upper ends of threaded removably and members that are carried in complementally threaded holes of said plate.

16. The apparatus of claim 14, wherein said cutting members comprise hardened teeth that are brazed to bolt heads.

17. The apparatus of claim 14, wherein a plurality of sub-plate sections are removably carried by said plate,

with a plurality of cutting teeth secured to each said sub-plate section.

18. The apparatus of claim 17, wherein said subplate sections comprise substantially identical pieshaped portions of a disk-like plate. 

1. In a pulping tank adapted for the pulping of debris and the like, comprising pulping tank means for receiving debris and liquid therein, sizing ring means carried by and disposed annularly at the bottom of the tank for permitting the passage radially outwardly therethrough of desirably sized pulped debris, said sizing ring means having a plurality of holes therethrough of predetermined size, generally horizontal impeller plate means disposed at the bottom of said tank means and having cutting elements on an upper surface thereof for impelling debris therein with rotary motion of said impeller means, radially outwardly through holes in said sizing ring means, an uppermost surface portion of said impeller plate means being disposed lower than said sizing ring means, inwardly of said sizing ring means with downwardly extending cutting means being carried by said sizing ring means and cutting means being carried by said impeller means, and with said disposition of said impeller plate upper surface and said cutting means defining means facilitating the passage of debris particles in radially directed straight lines across said plate means upper surface and under said sizing ring means through a cutting zone defined by said cutting means.
 1. In a pulping tank adapted for the pulping of debris and the like, comprising pulping tank means for receiving debris and liquid therein, sizing ring means carried by and disposed annularly at the bottom of the tank for permitting the passage radially outwardly therethrough of desirably sized pulped debris, said sizing ring means having a plurality of holes therethrough of predetermined size, generally horizontal impeller plate means disposed at the bottom of said tank means and having cutting elements on an upper surface thereof for impelling debris therein with rotary motion of said impeller means, radially outwardly through holes in said sizing ring means, an uppermost surface portion of said impeller plate means being disposed lower than said sizing ring means, inwardly of said sizing ring means with downwardly extending cutting means being carried by said sizing ring means and cutting means being carried by said impeller means, and with said disposition of said impeller plate upper surface and said cutting means defining means facilitating the passage of debris particles in radially directed straight lines across said plate means upper surface and under said sizing ring means through a cutting zone defined by said cutting means.
 2. The apparatus of claim 1, wherein said sizing ring means comprises an annular screen having an annular shape-retaining ring carried at the lower end thereof.
 3. In a pulping tank adapted for the pulping of debris and the like, comprising pulping tank means for receiving debris and liquid therein, sizing ring means carried by and disposed annularly at the bottom of the tank for permitting the passage radially outwardly therethrough of desirably sized pulped debris, said sizing ring means having a plurality of holes therethrough of predetermined size, impeller plate means disposed at the bottom of said tank means for impelling debris therein with rotary motion of said impeller means, radially outwardly through holes in said sizing ring means, an uppermost surface portion of said impeller plate means being disposed lower thAn said sizing ring means, inwardly of said sizing ring means with downwardly extending cutting means being carried by said sizing ring means and cutting means being carried by said impeller means, and with said disposition of said impeller plate upper surface and said cutting means defining means facilitating the passage of debris particles in radially directed straight lines across said plate means upper surface and under said sizing ring means through a cutting zone defined by said cutting means, wherein said impeller plate means comprises a vertically stepped plate, with an annular outermost portion having an upper surface disposed lower than said uppermost surface portion of said impeller plate.
 4. The apparatus of claim 3, wherein said cutting means carried by said impeller means and said sizing ring means comprise oppositely directed teeth mounted with their apices to each respectively define a locus of points, each such locus of points describing a circle of different diameter.
 5. The apparatus of claim 3, wherein the distance between the circumferential inner and lower edge of said sizing ring means and the circumferential outer edge of said uppermost surface portion of said impeller plate means is of a predetermined dimension selected in accordance with the maximum size of particles desired to be passed therebetween.
 6. The apparatus of claim 4, wherein the distance between the circumferential inner and lower edge of said sizing ring means and the circumferential outer edge of said uppermost surface portion of said impeller plate means is of a predetermined dimension selected in accordance with the maximum size of particles desired to be passed therebetween.
 7. The apparatus of claim 5, wherein said distance is approximately one-fourth inch.
 8. The apparatus of claim 5, wherein said distance is approximately three-sixteenths inch.
 9. A pulping tank adapted for the pulping of debris and the like, comprising a container having an upstanding cylindrical wall and an incomplete bottom wall comprising an annular radially inwardly directed protrusion from said cylindrical wall, with a rotatably driveable impeller plate disposed substantially inwardly thereof and spaced below said protrusion, with a perforated sizing ring between said plate and protrusion for passing therethrough particles impelled outwardly upon rotation of said plate, said impeller plate being provided with abrading teeth disposed on the upper surface thereof, comprising an outer annular abrading surface portion located outwardly of a non-abrading central portion of said plate, including means comprising a component of said tank for creating a predetermined liquid vortex in the tank upon rotation of said impeller plate at a predetermined speed, such that the vortex has a central cavity, the bottom of which extends to the impeller plate and defines an area greater than said non-abrading portion of said plate.
 10. The apparatus of claim 9, wherein said abrading surface portion comprises a toothed surface portion, and said non-abrading portion comprises an untoothed portion.
 11. The apparatus of claim 9, wherein said latter means comprises said incomplete bottom wall being substantially normal to said upstanding cylindrical wall.
 12. The apparatus of claim 9, wherein said latter means comprises projection means upstanding from inner portions of bottom wall.
 13. The apparatus of claim 11, including projection panel means upstanding from inner portions of said bottom wall, wherein said projection panel means comprises a plurality of individual members protruding upwardly from said bottom wall, each having upper surfaces sloped upwardly from the bottom wall to free ends thereof, with said sloped surfaces facing in opposition to the predetermined direction of debris travel in the tank comprising means facilitating travel of debris over said members, with said members being circumferentially arranged on said bottom wall.
 14. In a pulping tank adapted for the pulping of debris and the liKe, comprising pulping tank means for receiving debris and liquid therein, sizing ring means carried by and disposed annularly at the bottom of the tank for permitting the passage radially outwardly therethrough of desirably sized pulped debris, said sizing ring means having a plurality of holes therethrough of predetermined size, impeller plate means disposed at the bottom of said tank means for impelling debris therein with rotary motion of said impeller plate means, radially outwardly through holes in said sizing ring means, an uppermost surface portion of said impeller plate means being disposed lower than said sizing ring means, inwardly of said sizing ring means with downwardly extending cutting means being carried by said sizing ring means and cutting means being carried by said impeller means, and with said disposition of said impeller plate upper surface and said cutting means defining means facilitating the passage of debris particles in radially directed straight lines across said plate means upper surface and under said sizing ring means through a cutting zone defined by said cutting means, and wherein said impeller plate means comprises a plate having a centrally disposed drive shaft connected thereto, and cutting members removably and replaceably carried by said plate.
 15. The apparatus of claim 13, wherein said cutting members are connected to upper ends of threaded members that are carried in complementally threaded holes of said plate.
 16. The apparatus of claim 14, wherein said cutting members comprise hardened teeth that are brazed to bolt heads.
 17. The apparatus of claim 14, wherein a plurality of sub-plate sections are removably carried by said plate, with a plurality of cutting teeth secured to each said sub-plate section. 